President Donald Trump is "systematically trying to destroy the structure of our federal government," according to Pulitzer Prize-winning investigative journalist David Cay Johnston.

"If you don't question whether Donald Trump has divided loyalties, I think you're not thinking carefully about who Donald Trump is and what he himself has said," Johnston told MSNBC's "Morning Joe" co-hosts Joe Scarborough and Mika Brzezinski.

Scarborough then asked: "How is he making it worse?"

"They're systematically trying to destroy the structure of our federal government," Johnston said. "The Trump administration has loosed what I call 'political termites' into the structure, just as termites will eat away at your home until you suddenly discover it's terribly damaged.

"Most ambassadorships are empty and that means that in Saudi Arabia and Jordan and a lot of other countries that are important to our national security, there's no U.S. ambassador at the table listening and hearing, and where big business deals are made, there's no U.S. ambassador who's there."

He added later that "Donald has spent his whole life thumbing his nose at the law…. He spent years deeply entangled with an international drug trafficker and there's no explanation for why he would do what he did although everything he did makes sense if he was in business with this drug trafficker. Donald has beaten four grand juries, he's had two civil trials for tax fraud, both of which he lost. He's confessed to being a sales tax cheat. He's been found by a judge to have engaged in a conspiracy to cheat workers out of their pay. The man has spent his entire life being a con artist and he runs the White House the same way and he doesn't know anything."

"The single most important thing is Donald Trump will tell you 'I'm smart, I'm like a smart person.' No, he's not. He wasn't smart when I met him in 1988 and he's appallingly ignorant. He doesn't know a Sunni from a Shi'a and why it matters."

Johnston continued later, saying that Trump is "unqualified, he's never done a day of public service. He's not well informed, he's not very smart, he's not a strategic thinker. There are law professors who use Trump as an example. He's not a cooperative negotiator."